UART¶

UART Overview¶

The DART-MX95 exposes up to eight LPUART interfaces, some of which are multiplexed with other peripherals.

Serial Port	Device Node	Device Tree	DART-MX95 / Sonata Board	DART-MX95 / DT8MCustomBoard
UART1	/dev/ttyLP0	lpuart1	A55 debug serial console ^[1]	A55 debug serial console ^[1]
UART2	/dev/ttyLP1	lpuart2	Requires device tree configuration. Connected to (J7.20, J8.4)	Requires device tree configuration. Connected to (J13.20, J14.4)
UART3	/dev/ttyLP2	lpuart3	Requires device tree configuration. Connected to (J6.11, J6.13) ^[2]	Requires device tree configuration. Connected to (J12.11, J12.13) ^[2]
UART4	/dev/ttyLP3	lpuart4	Requires device tree configuration. Refer to the datasheet for the LPUART4 signals	Requires device tree configuration. Refer to the datasheet for the LPUART4 signals
UART5	/dev/ttyLP4	lpuart5	1.8V Signal level, used on SOM for Bluetooth interface and is accessible only when Bluetooth is disabled. ^[3]	1.8V Signal level, used on SOM for Bluetooth interface and is accessible only when Bluetooth is disabled. ^[3]
UART6	/dev/ttyLP5	lpuart6	Requires device tree configuration. Refer to the datasheet for the LPUART6 signals	Requires device tree configuration. Refer to the datasheet for the LPUART6 signals
UART7	/dev/ttyLP6	lpuart7	Requires device tree configuration. Refer to the datasheet for the LPUART7 signals	Requires device tree configuration. Refer to the datasheet for the LPUART7 signals
UART8	/dev/ttyLP7	lpuart8	Connected to (J6.4, J6.6) ^[4]	Connected to (J12.4, J12.6) ^[4]

↑ When OEI is built with DEBUG enabled, lpuart1 is used as the OEI debug UART. This is enabled by default and does not conflict with the A55 serial console.
↑ When Cortex-M7 support is enabled, lpuart3 is used as the Cortex-M7 debug console.
↑ See Disabling Bluetooth / Enabling UART5 (/dev/ttyLP4)
↑ When System Manager is built with the debug configuration, lpuart8 is used as the Cortex-M33 debug console.

UART5/ttyLP4 is used by the Bluetooth on the SOM. To use it on the carrier board, Bluetooth must be disabled on the SOM.

First, disable variscite-bt by running:

systemctl stop variscite-bt; systemctl stop variscite-ot
systemctl disable variscite-bt; systemctl disable variscite-ot

Then, disable Bluetooth in the device tree imx95-var-dart.dtsi:

&lpuart5 {
   ...
    bluetooth {
        compatible = "nxp,88w8987-bt";
        status = "disabled";
    };
   ...
};

The following demonstrates how to test UART8 on the DART-MX95 DT8MCustomboard following the table above.

Short J12.4 and J12.6 pins and run the following commands:

stty -F /dev/ttyLP7 -echo -onlcr 115200
cat /dev/ttyLP7 &
echo hello > /dev/ttyLP7

For each invocation of the echo command the "hello" string should appear on the terminal.